/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */
package wx.xml.xalan.xalan.extensions;

import java.io.IOException;
import java.util.Vector;

import javax.xml.transform.TransformerException;

import wx.xml.xalan.xalan.templates.ElemTemplateElement;
import wx.xml.xalan.xalan.templates.Stylesheet;
import wx.xml.xalan.xalan.transformer.TransformerImpl;
import wx.xml.xalan.xpath.functions.FuncExtFunction;

/**
 * Abstract base class for handling an extension namespace for XPath.
 * Provides functions to test a function's existence and call a function.
 * Also provides functions for calling an element and testing for
 * an element's existence.
 *
 * @author Sanjiva Weerawarana (sanjiva@watson.ibm.com)
 * @xsl.usage internal
 */
public abstract class ExtensionHandler {

    /**
     * uri of the extension namespace
     */
    protected String m_namespaceUri;

    /**
     * scripting language of implementation
     */
    protected String m_scriptLang;

    /**
     * Construct a new extension namespace handler given all the information
     * needed.
     *
     * @param namespaceUri the extension namespace URI that I'm implementing
     * @param scriptLang   language of code implementing the extension
     */
    protected ExtensionHandler(String namespaceUri, String scriptLang) {
        m_namespaceUri = namespaceUri;
        m_scriptLang = scriptLang;
    }

    /**
     * This method loads a class using the context class loader if we're
     * running under Java2 or higher.
     *
     * @param className Name of the class to load
     */
    static Class getClassForName(String className)
        throws ClassNotFoundException {
        // Hack for backwards compatibility with XalanJ1 stylesheets
        if (className.equals("wx.xml.xalan.xalan.xslt.extensions.Redirect")) {
            className = "wx.xml.xalan.xalan.lib.Redirect";
        }

        return ObjectFactory.findProviderClass(
            className, ObjectFactory.findClassLoader(), true);
    }

    /**
     * Tests whether a certain function name is known within this namespace.
     *
     * @param function name of the function being tested
     * @return true if its known, false if not.
     */
    public abstract boolean isFunctionAvailable(String function);

    /**
     * Tests whether a certain element name is known within this namespace.
     *
     * @param element Name of element to check
     * @return true if its known, false if not.
     */
    public abstract boolean isElementAvailable(String element);

    /**
     * Process a call to a function.
     *
     * @param funcName    Function name.
     * @param args        The arguments of the function call.
     * @param methodKey   A key that uniquely identifies this class and method call.
     * @param exprContext The context in which this expression is being executed.
     * @return the return value of the function evaluation.
     * @throws TransformerException if parsing trouble
     */
    public abstract Object callFunction(
        String funcName, Vector args, Object methodKey,
        ExpressionContext exprContext) throws TransformerException;

    /**
     * Process a call to a function.
     *
     * @param extFunction The XPath extension function.
     * @param args        The arguments of the function call.
     * @param exprContext The context in which this expression is being executed.
     * @return the return value of the function evaluation.
     * @throws TransformerException if parsing trouble
     */
    public abstract Object callFunction(
        FuncExtFunction extFunction, Vector args,
        ExpressionContext exprContext) throws TransformerException;

    /**
     * Process a call to this extension namespace via an element. As a side
     * effect, the results are sent to the TransformerImpl's result tree.
     *
     * @param localPart      Element name's local part.
     * @param element        The extension element being processed.
     * @param transformer    Handle to TransformerImpl.
     * @param stylesheetTree The compiled stylesheet tree.
     * @param methodKey      A key that uniquely identifies this class and method call.
     * @throws XSLProcessorException thrown if something goes wrong
     *                               while running the extension handler.
     * @throws MalformedURLException if loading trouble
     * @throws FileNotFoundException if loading trouble
     * @throws IOException           if loading trouble
     * @throws TransformerException  if parsing trouble
     */
    public abstract void processElement(
        String localPart, ElemTemplateElement element, TransformerImpl transformer,
        Stylesheet stylesheetTree, Object methodKey) throws TransformerException, IOException;
}
